configure.ac: add --enable-numa switch

Before the change ./configure detected numa support automatically
withoun a nice way to disable autodetection.

The change adds `--enable-numa` / `--disable-numa` switch to
override the default. If `--enable-numa` is passed and `libnuma`
is not present then configure will fail.

Reported-by: Sergey Alirzaev
Bug: https://github.com/gentoo-haskell/gentoo-haskell/issues/955


Signed-off-by: Sergei Trofimovich <slyfox@gentoo.org>

configure.ac

@@ -1265,11 +1265,22 @@ AC_DEFINE_UNQUOTED([USE_LIBDW], [$USE_LIBDW], [Set to 1 to use libdw])
 dnl ** Have libnuma?
 dnl --------------------------------------------------------------
 HaveLibNuma=0
-AC_CHECK_HEADERS([numa.h numaif.h])
+AC_ARG_ENABLE(numa,
+    [AC_HELP_STRING([--enable-numa],
+        [Enable NUMA memory policy and thread affinity support in the
+         runtime system via numactl's libnuma [default=auto]])])
 
-if test "$ac_cv_header_numa_h$ac_cv_header_numaif_h" = "yesyes" ; then
+if test "$enable_numa" != "no" ; then
+  AC_CHECK_HEADERS([numa.h numaif.h])
+
+  if test "$ac_cv_header_numa_h$ac_cv_header_numaif_h" = "yesyes" ; then
     AC_CHECK_LIB(numa, numa_available,HaveLibNuma=1)
+  fi
+  if test "$enable_numa:$HaveLibNuma" = "yes:0" ; then
+      AC_MSG_ERROR([Cannot find system libnuma (required by --enable-numa)])]
+  fi
 fi
+
 AC_DEFINE_UNQUOTED([HAVE_LIBNUMA], [$HaveLibNuma], [Define to 1 if you have libnuma])
 if test $HaveLibNuma = "1" ; then
   AC_SUBST([CabalHaveLibNuma],[True])